A fundamental question in neurobiology is how individual nerve cells make and maintain appropriate contact with other neurons. There are a number of ways to approach this question. I have chosen to perturb a simple nervous system surgically and monitor the connections among identified nerve cells during the subsequent two week period of behavioral recovery. Specifically, I record from neurons in a single leech ganglia that has been surgically isolated from the rest of the nervous system. Within two weeks, the single innervated segment acquires the ability to make swimming movements, an ability that previously required the whole nervous system. I will use electrophysiological and structural techniques to assess the changes that have taken place in the individual nerve cells and the connections between them. Hopefully these experiments will not only give insights into the fundamental mechanisms by which nerve cells determine their pattern of interconnection but will also have the practical benefit of suggesting ways to treat central nervous system injuries more effectively.